Oxide removing bath



Patented Oct. 13, 1953 2,655,481 OXIDE REMOVING BATH Irvine 0. Eastern Cling-an, Stainless Baltimore, Md., assignor to Steel Corporation, Baltimore, d

d., a corporation of Marylan No Drawing. Application April 4, 1949, Serial No. 85,466

1 Claim. (Cl. 252135) The present invention relates to the cleaning of metals, notably stainless steels.

More particularly, this invention provides A further object is to provide such a bath that possesses a combination of beneficial properties mum softening ability.

A still further object is to provide a molten bath conslsting of an anhydrous mixture of causamount of a stabilizing agent, e. g. borax, which agent acts to not only stabilize the bath but also to rejuvenate the bath.

Various other objects and advantages of this invention will become apparent from the following description.

The use of molten sodium and/ or potassium hydroxides from temperatures ranging from 600 F. to 1000 F. has been employed for a number of peratures ranging from 600 to 1000 F. has been found to be very beneficial in efiecting the partial removal of this type of scale.

is removed from the molten solution and rapidly quenched in water. The reaction between the hot alkali metal hydroxides and the water, pro

duces super-heated steam that further shatters The My invention provides a method for stabilizing the nitrate radical of a molten-caustic-nitrate bath without impairing, in any manner, the oxidizing capacity of the nitrate radical under the conditions of use. I have discovered that small inclusions of sodium borate in the present in the bath may by weight of the total be from about 0.1 to 4% as indicated above the weight of the bath, and

parts by weight sodium hydroxide 10 parts by weight sodium nitrate 4 parts by weight sodium borate (Na2B4O710H2O') tween 830 F. and 870 F., preferably 850 F. for approximately eight minutes. Next, the metal for five to seven minutes in another customary by Weight by weight hydrofluoric acid at F. to F Again the metal is removed and washed in cold running water.

smooth, uniform, of maximum cleanness, and very pleasing in surface appearance. It has also been found that the surface of this metal has been improved in its resistance to rusting or corrosion and to its reception of surface coatings of various sorts. Further, the provision of the small amount of sodium borate clearly improves the stability of the bath and aids in regenerating the nitrate content of the bath.

The words employed. in this specification are for the purpose of description and not of limitation. The scope of the invention is set forth in the claim.

I claim:

A molten bath for removing oxides from the surface of metals which comprises a fused sub- 5 amount of iron.

stantially a nhydrous mixture of 90 parts by weight of sodium hydroxide, 10 parts by weight of an alkali metal nitrate, and about .1 to 4 parts by weight of sodium borate and a spectroscopic IRVINE C. CLINGAN.

References Cited in the file of this patent UNITED STATES PATENTS V 10 Number Name Date Spence et al June 3, 194? Bellis Aug. 13, 1929 McKay Jan. 27, 1942 Webster et al Jan. 11, 1949 

